The present invention generally relates to a power apparatus to be used in an arc welding device, and more particularly, to the control operation thereof at a welding start time.
In order to obtain a better arc start performance in an arc welding device, conventionally there has been adopted a hot starting system in which an increased voltage is applied between a welding wire and a mother material during a start operation, the increased voltage being higher than that during the welding operation when a welding current flows between the welding wire tip end portion and the mother material. A wire slow down system has also been adopted in which the feed rate of the welding wire during a welding start operation is slower than that during the welding operation.
When the welding wire tip end portion has been heated to a red hot condition, the arc starting operation is comparatively easy to effect than a case where the welding wire tip end portion has been cooled.
When a next welding operation has been started with the welding wire tip end portion being still heated to a red hot condition after a prior welding has been completed, in the conventional systems, an excessive current is applied to the welding wire thus causing the welding wire to burn or the arc to break, or adversely influencing the bead shape. Further, the conventional wire slow down system has a problem in that the overall welding operation time cannot be shortened due to the slower welding wire feed quantity during a period from the welding start to the flow of the welding current between the welding wire and the mother material even though the red not condition of the welding wire tip end portion remains from the prior welding.